A liquid crystal display belongs to a display product of dynamic scanning type. When displaying one-frame picture, the liquid crystal display scans pixels one row by one row, and enables human eyes to feel a displayed one-frame picture by utilizing human eyes' visual residual effect, so as to realize displaying of the entire picture. Therefore, in the process of normal display of the liquid crystal display, at each time point, a gate line signal of only one gate line is a scanning signal (for example, high voltage) to scan its corresponding pixel row, while gate line signals of remaining gate lines are non-scanning signals (for example, low voltage).
However, when the liquid crystal display is started up, it needs to initialize a gate line signal of each gate line to a low voltage (VGL) so as to initialize all the pixel rows to a non-scanning state, which thus cause that the current of a power supply voltage terminal providing a low voltage becomes very large in a moment; on the other hand, when the liquid crystal is shut down, for the reasons of eliminating shut-down image sticking and protecting the liquid crystal display and so on, it requires to put a gate line signal of each gate line at a high voltage (VGH), such that all the pixel rows are in a scanned state so as to realize quick discharging of all the pixels. At this time, it would result in that the current of the power supply voltage terminal providing a high voltage becomes very large in a moment.
Since the liquid crystal display causes the output current of the power supply voltage terminal that provides the low voltage (VGL) or the high voltage (VGH) to become very large when being started up or shut down, it then results in that a load of a power supply chip that provides the low voltage (VGL) or the high voltage (VGH) becomes very large in a moment, and also makes that the input current received by a power supply input terminal of the power supply chip from an external power supply becomes large in a moment, which is easy to cause the power supply chip damaged, a connection wire between a power supply input terminal of a power supply chip on the liquid crystal display panel and an external power supply burned out, and a fuse wire on the liquid crystal display panel damaged.
Therefore, a gate drive device which is capable of reducing current impact when the liquid crystal display is started up or shut down is needed.